This build is ok but it doesn't quite make optimal use of the true source of damage for fire crusaders which is the stacking aspect of the Akarat's Champion - Fire Starter DoT. The more sources of damage you have going at once the more it stacks with itself. As a result, Heaven's Fury - Blessed Ground will significantly increase your damage over Falling Sword - Superheated not just because it ticks more rapidly with two sources (beam and the ground based DoT) but also because it costs no wrath (big deal for a build that can frequently be wrath starved) and has a base cooldown 10 seconds shorter than Falling Sword. These three factors really put Falling Sword - Superheated behind even though it is fire damage.I find this kind of unfortunate as I like Falling Sword thematically for this build but until it receives some rebalancing, possibly in the form of something like shorter cooldown/animation or cheaper/no wrath cost, it will seriously underperform.

As for Maximus, it is fun but you will find that it too underperforms compared to Darklight for the build. The most important thing is having sources of damage to stack your Fire Starter DoT and Darklight gives you another fairly reliable one, it also gives you 15% IAS and 15% CDR from using Fervor over Heavenly Strength. On top of that the demon is fragile and the damage from the chain snapshots things like % damage buffs (such as the one from Akarat's Champion or the buff from Harrington's) at the time of summoning which can make getting the most out of your demon friend difficult/impossible since it is a random proc.